Fix $border-radius-base SCSS value

This variable was using the value 3px which is not in line
with our Pajama's 8px spacing system

app/assets/stylesheets/bootstrap_migration.scss

@@ -6,7 +6,7 @@ $brand-info: $blue-500;
 $brand-warning: $orange-500;
 $brand-danger: $red-500;
 
-$border-radius-base: 3px !default;
+$border-radius-base: $gl-border-radius-base;
 
 $modal-body-bg: $white;
 $input-border: $border-color;

changelogs/unreleased/cngo-fix-border-radius-base.yml

+---
+title: Fix border-radius-base SCSS value
+merge_request: 35740
+author:
+type: fixed